1. Field of the invention
The present invention relates to a multipolar dc motor having an improved brush arrangement, and more particularly, to the brush arrangement having a relatively large section area brush for large current and sufficient space for arranging components.
2. Prior art
One type of conventional six-pole dc motor having armature coil wound in the manner of double-layer wave windings known in the art comprises a pair of positive brushes and a pair of negative brushes. These four brushes are circumferentially disposed around a commutator at prescribed angular intervals, and are in sliding electrical contact with the commutator. The positive brushes are 120 degrees apart, and the negative brushes are also 120 degrees apart. A positive brush and an adjacent negative brush are 60 degrees apart, and another positive brush and another adjacent negative brush are also 60 degrees apart.
In the conventional dc motor mentioned above, however, each space between the positive brush and the adjacent negative brush is very tight to dispose the springs and the brush holders, therefore, the width of the brush holder is restricted from the space. Also, the width of the brush is restricted from the width of the brush holder, so that the section area of the brush is restricted. Because of this, the current density of the brush is at a higher level relation to the rated current density, so that the durability of the brush is relatively low.